Database handle for the object. It is of XML type ID, so is constrained to beunique in the XML document within which it occurs. An external identifier for the object inthe form of a URI may be constructed using standard XML and XPointer methods. This is doneby concatenating the URI for the document, a fragment separator, and the value of the idattribute.
The uom attribute provides an identifier of the unit of measure used forthis coordinate system axis. The value of this coordinate in a coordinate tuple shallbe recorded using this unit of measure, whenever those coordinates use a coordinatereference system that uses a coordinate system that uses this axis.
Source
<element name="CoordinateSystemAxis" type="gml:CoordinateSystemAxisType" substitutionGroup="gml:Definition"><annotation><documentation>gml:CoordinateSystemAxis is a definition of a coordinate system axis.</documentation></annotation></element>